Lipidation and PEGylation Strategies to Prolong the Half-Life of a Nanomolar EphA4 Receptor Antagonist.

The EphA4 receptor tyrosine kinase plays a role in neurodegenerative diseases, inhibition of nerve regeneration, cancer progression and other diseases. Therefore, EphA4 inhibition has potential therapeutic value. Selective EphA4 kinase inhibitors are not available, but we identified peptide antagonists that inhibit ephrin ligand binding to EphA4 with high specificity. One of these peptides is the cyclic (βAPYCVYRβASWSC-NH), which inhibits ephrin-A5 ligand binding to EphA4 with low nanomolar binding affinity and is highly protease resistant. Here we describe modifications of that yield two different key derivatives with greatly increased half-lives in the mouse circulation, the lipidated and the PEGylated . These two derivatives inhibit ligand induced EphA4 activation in cells with sub-micromolar potency. Since they retain high potency and specificity for EphA4, lipidated and PEGylated derivatives represent new tools for discriminating EphA4 activities and for preclinical testing of EphA4 inhibition in animal disease models.